Thousands of people are killed or injured annually in motor vehicle accidents wherein the vehicle driver and/or passengers are thrown forward as a result of the initial, i.e., primary, collision so as to impact against the solid surfaces forming the interior of the vehicle. As a result, passive restraint systems adapted for use with such vehicles have been developed for the purpose of reducing or eliminating these injuries and/or deaths.
One system which has been extensively investigated senses rapid vehicle deceleration, such as that which occurs upon a primary impact between an automobile and, for example, another vehicle. Upon receipt of a signal from a remote sensor device, the system initiates inflation of an expandable passive restraint, i.e., an air bag, prior to the occurrence of any secondary collision between the driver and/or passengers and the interior of the automobile. The expandable restraint is normally inflated by the combustion products produced by a pyrotechnic gas generator, i.e., inflator, device (Note: the terms "gas generator" and "inflator" are used interchangably herein). This restraint is interposed between the interior surface of the automobile and one or more occupants of the vehicle. The air bag must therefore be inflated within milliseconds of the primary impact in order to ensure that the vehicle occupants' forward motion is arrested before injury occurs due to the secondary collisions against the adjacent solid interior surfaces.
Moreover, it is additionally desirable to ensure deflation of the restraining device as soon as the force of a crash is expended, so that the occupant(s) do not thereafter become trapped within the vehicle subsequent to the collision. In order to meet such criteria, specifications have been established whereby the expandable bag should be sufficiently inflated to restrain a vehicle occupant in about 30-60 milliseconds after initiation, with substantial deflation occurring after about 100 milliseconds.
Moreover, as is well understood by those practicing in this art, pyrotechnic inflators such as those described above may be fabricated and/or adapted in a variety of different configurations depending upon the particular response characteristics required for the intended application. One particularly important consideration in this regard is as to whether the inflator unit is to be mounted upon the steering wheel to restrain the vehicle operator, or whether it is intended to protect, for example, the front seat passengers. In the latter case, the device is normally installed within the vehicle's dashboard adjacent the passenger side of the vehicle. A different set of requirements must be met depending upon which mode of use is intended.
That is, an inflator unit intended for installation on the driver's side, e.g., within the steering assembly, of an automobile must be smaller in size than a passenger side unit to enable it to fit within the steering wheel. It must additionally generate a gaseous combustion product up to two times faster than a passenger side unit due to the minimal separation between the driver and the steering wheel in comparison to the available space between the body of a passenger within the vehicle and the vehicle's dashboard. Moreover, a passenger side inflator device is required to produce up to four times as much gas as a driver's side inflator to completely inflate the correspondingly larger passenger side air bag. This increase in bag size is necessitated due to the relatively larger volume of space within the vehicle in which the passenger may be found, as opposed to the driver who is "locked" into a position behind the steering wheel. Numerous examples of passenger side inflator devices are known in the prior art, such as that disclosed, for example, in U.S. Pat. No. 4,005,876 to Jorgensen et al.
Commonly encountered features among pyrotechnic gas generators utilized within motor vehicle passive restraint devices of the type described above include: (1) an outer metal housing, e.g., of steel or aluminum, (2) a gas generant composition located within the housing, (3) means to ignite the gas generant responsive to a signal received from a sensor positioned at a location removed from the inflator, and (4) means to filter and to cool the gas, positioned between the propellant composition and a plurality of gas discharge ports, i.e., orifices defined by the generator housing.
Such pyrotechnic gas generators must be capable of withstanding enormous thermal and mechanical stresses for a short period during the gas generation process. Thus, most inflators that have been and are currently being used with automobile air bag devices are commonly fabricated using heavy gauge steel for the casing and other structural housing components, with these components being joined together by, for example, threaded screws, roll crimping or welding. The recent emphasis on weight reduction for the purpose of fuel conservation in motorized vehicles has, however, created a need and a demand for a lighter weight inflation system. One example of such a system is illustrated in U.S. Pat. No. 4,547,342 to Adams et al. disclosing an aluminum driver's side inflator unit.
A further advance in the field of motor vehicle passive crash restraints involves the inclusion of aspiration means for drawing ambient air, e.g., from within the vehicle's passenger compartment into the air bag so as to cool the gas entering the bag from a pyrotechnic inflator operatively associated therewith. This arrangement thus permits a more rapid inflation of the air bag than would otherwise be possible upon utilizing only the gas produced by the inflator device.
Various types of aspirating inflators are known in the prior art. Generally speaking however, these devices are typically adapted for installation within the driver's side of the vehicle. For example, a number of references disclose arrangements wherein the interior of the air bag is in fluid communication with the atmosphere within the vehicle through a unidirectional valve. Such valves permit air from within the vehicle to enter the interior of the bag, thus facilitating its inflation. These valves subsequently prevent the atmosphere within the bag from venting back out along the same path, thus requiring the provision of some means (e.g., such as vents or blow-out patches) for permitting the gasses to escape through the fabric of the bag itself. Examples of air bag systems of the type described above may be found in U.S. Pat. Nos. 3,675,942 to Huber; 3,767,225 to Mazelsky; 3,773,350 and 3,791,666 to Shibamoto; 3,788,663 to Weman; and 3,909,037 to Stewart.
Alternately, a number of other references disclose air bag inflator assemblies wherein the flow of ambient atmosphere proceeds in two directions, i.e., initially, from within vehicle into the air bag and then, subsequent to the collision, gradually back into the interior of the vehicle, so as to facilitate the deflation of the air bag as well. Air bag devices of this type are disclosed, for example, in U.S. Pat. Nos. 3,762,741 and 3,784,225 to Fleck et al.; 3,773,351 to Catanzarite; 3,843,152 to Nonaka and 3,910,595 to Katter et al.
In a further alternate arrangement, ambient air from within the vehicle is initially aspirated into the air bag upon initiation of the system response due to the occurrence of a collision, following which the entire contents of the bag, comprising the gaseous products supplied by the inflator in admixture with the ambient atmosphere, is subsequently directed entirely out of the vehicle into the surrounding space. An example of this type of arrangement for a driver's side air bag apparatus is illustrated in U.S. Pat. No. Re 29,228 to Hass (i.e., a reissue of U.S. Pat. No. 3,632,133) wherein the air bag is inflated under the combined influence of a high velocity stream of gas produced by a pyrotechnic gas inflator device and a relatively large volume of air drawn into the bag by the passage of the high-velocity gas. The air may, if desired, be drawn from outside the vehicle through a conduit assembly extending through the steering column, and it may be subsequently discharged through the same conduit to the outside of the vehicle.
In addition, to facilitate the installation and maintenance of some air bag assemblies, they may be produced in modular form, as described for example, in U.S. Pat. No. 3,819,205 to Dunford et al. which discloses a driver's side air bag module.
Applicant is unaware, however, of any modularized air bag system for use on the passenger side of a motor vehicle which includes means, such as those described above, for aspirating ambient air, either from within or without the passenger compartment of the vehicle, and directing these additional gases into the air bag so as to facilitate the inflation thereof. Moreover, there is additionally no teaching in the prior art of such a modularized assembly wherein the gaseous mixture from within the air bag is vented completely out of the vehicle and into the surrounding space to facilitate deflation of the bag, while also avoiding the generation of an abrupt pressure increase within the vehicle which is known to be injurious to the occupants thereof.